Methyl N-methylanthranilate (DMA) is a valuable compound used in the flavouring and fragrance industry and is also reported to be a bird repellent described in patent U.S. Pat. No. 2,967,128.
Several methods are known for the preparation of DMA.
A classical route is N-methylation of methyl anthranilate with a methylating agent as dimethyl sulfate or methyl iodide, cited in patent DE 3936229. To avoid dimethylation, reductive methylation with formaldehyde and hydrogen has been described in patent U.S. Pat. No. 4,633,009. Reaction scheme 1.

To prepare methyl anthranilate, 2H-3,1-benzoxazine-2,4(1H)-dione (isatoic anhydride) is reacted under alkaline conditions
with methanol as disclosed in patent IN 146359. Reaction scheme 2.

As disclosed by Staiger, J. Org. Chem. (1959), 24, 1214-19, N-methylisatoic anhydride reacts with methanol under alkaline conditions to produce Methyl N-methylanthranilate.
Hardtmann, J. Heterocycl. Chem. (1975), 12 (3), 565-72 prepares N-substituted isatoic anhydride by reacting the N-sodium salt of isatoic anhydride, prepared from sodium hydride, with alkyl halides. The N-benzyl derivative of isatoic anhydride is prepared using potassium carbonate and benzyl chloride.